Acoustic damping for blower in cpap device / pap device with noise reducing enclosure

ABSTRACT

A CPAP device for delivering pressurized, humidified breathable gas for a patient includes a flow generator configured to pressurize a flow of breathable gas. The flow generator includes an air outlet and a removable water container configured to humidify the pressurized breathable gas received from the flow generator. The water container includes an air inlet and an air outlet. The CPAP device further includes a first elastomeric face seal configured to sealingly abut against a substantially flat portion of the water container surrounding the water container air inlet, the first elastomeric face seal being located at an intermediate position between the flow generator air outlet and the water container air inlet when the water container is placed into position to pneumatically communicate with the flow generator. In addition, the CPAP device includes a second elastomeric face seal, a portion of which is configured to sealingly abut against a substantially flat external surface portion of the water container surrounding the water container air outlet.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/054,820, filed Feb. 26, 2016, now pending, which is a continuation ofU.S. application Ser. No. 14/790,693, filed Jul. 2, 2015, now U.S. Pat.No. 9,358,359, which is a continuation of U.S. application Ser. No.14/501,253, filed Sep. 30, 2014, now U.S. Pat. No. 9,072,860, which is acontinuation of U.S. application Ser. No. 12/659,963, filed Mar. 26,2010, now pending, which is a continuation of U.S. application Ser. No.10/533,940, filed Dec. 29, 2006, now U.S. Pat. No. 8,006,691, which is anational phase application of PCT/AU2004/000810, filed Jun. 21, 2004 inEnglish and designating the United States, which claims the benefit ofAustralian Application No. 2003903139, filed Jun. 20, 2003, AustralianApplication No. 2003905136, filed Sep. 22, 2003, and AustralianApplication No. 2004901008, filed Feb. 27, 2004, each incorporatedherein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This invention relates to breathable gas supply apparatus, andparticularly but not exclusively to such apparatus for use in ContinuousPositive Airway Pressure (CPAP) treatment of conditions such asObstructive Sleep Apnea (OSA) and other respiratory disorders anddiseases such as emphysema. It will be described herein in itsapplication to CPAP treatment apparatus, but it is to be understood thatthe features of the invention will have application to other fields ofapplication, such as mechanical ventilation and assisted respiration.

2. Description of Related Art

CPAP treatment of OSA, a form of Noninvasive Positive PressureVentilation (NIPPV), involves the delivery of a pressurised breathablegas, usually air, to a patient's airways using a conduit and mask. Gaspressures employed for CPAP typically range from 4 cm H₂O to 28 cm H₂O,at flow rates of up to 180 L/min (measured at the mask), depending onpatient requirements. The pressurised gas acts as a pneumatic splint forthe patient's airway, preventing airway collapse, especially during theinspiratory phase of respiration.

CPAP machines comprising an air flow generator for supplying pressurisedair to the patient are known, and over recent years there has beencommercial imperative for more compact CPAP machines. However, inseeking to reduce the size of the CPAP machines there has been atrade-off between reduced size on the one hand and reduced performanceand/or increased noise on the other, for exampleMalinckrodt/Tyco/Puritan Bennett ‘Goodnight’ Series.

The advantages of incorporating humidification of the air supply to apatient are known, and CPAP machines are known which incorporatehumidifying devices, either separately from the flow generator orintegrated therewith. An example of an integrated flowgenerator/humidifier unit is the ResMed® S7 sold by the presentApplicant.

Another problem with some flow generators is extensive use of foam inthe air path for sound absorption. The foam can degrade with time.

SUMMARY OF THE INVENTION

One of the objects of the invention is to provide a simple and compactbreathable gas supply apparatus incorporating a humidifier which issimple and economic in its construction, compact, and easy to use. Otherobjects and advantages of the invention will be described throughout thespecification.

It is to be understood that apparatus described herein contains a numberof advances on the prior art, many of which are independent inventions,although they contribute together to the realisation of the generalobject expressed above.

The apparatus described herein incorporates novel aspects ofarchitecture of both the flow generator and the humidifier, and of theirintegration, which contribute to a reduction in size compared with knownunits having similar performance. Techniques for noise reduction anddamping are described which enable such a smaller machine to have noiseperformance which is at least as good as known larger machines.

The apparatus described herein achieves full integration of thehumidifier with the flow generator, in the sense that air flow,electrical and, if required, data connection between the flow generatorand the humidifier are provided automatically upon the physicalengagement of the two devices, without the need for any other process ofinterconnection.

In such an integrated device, provisions to guard against flowback ofwater from the humidifier tank to the flow generator are important, andnovel sealing arrangements, and novel arrangements for minimising theoccurrence of flowback while at the same time improving the uptake ofwater vapour in the humidifier are also described. The humidifier isreadily detached and replaced on the machine, and has very few parts tobe disassembled during cleaning.

Also described herein are improved, modular, devices for enabling dataconnection with the apparatus, including the connection of data storagedevices such as memory cards, smart cards, communication ports and thelike to be selectively attached by the user or by medical personnel.

Another aspect of the invention is to reduce or eliminate the use offoam in the air path.

In one form, the invention provides a flow generator unit for deliveringbreathable gas to a patient, including:

-   -   a flow generator case;    -   a powered gas flow generator within the case;    -   a power supply unit adapted for drop-in assembly in said case,        said power supply unit including a printed circuit board, a        power input connector rigidly attached to said printed circuit        board and a power output connector, and    -   a power supply unit mounting for mounting said power supply unit        in said case such that said power input connector aligns with a        power input port of said case.

A further form of the invention provides a blower enclosure for a flowgenerator used in delivery of breathable gas to a patient, said blowerenclosure including a metal container overmoulded with an acousticallydamping polymer lining.

A further form of the invention provides a blower enclosure for a flowgenerator used in delivery of breathable gas to a patient, said blowerbeing adapted to reduce noise from the enclosed blower, said enclosurecomprising:

-   -   a cavity within a chassis of the flow generator, the cavity        defined by side walls and base, the enclosure being adapted to        receive and mount a blower in said cavity and    -   a lid adapted to be mounted on said chassis so as to form a top        surface of the cavity,

-   wherein at least one of the chassis and lid is moulded from a    composite comprising a metal and a plastic.

A further form of the invention provides a blower for a flow generatorused in delivery of breathable gas to a patient, said blower comprisingan electric motor with a shaft, an impeller adapted to be mounted on theshaft, and a volute having an air-inlet and an air-outlet, the volutedefining a chamber in which a flow of air at pressure is developed, thevolute being moulded from a composite comprising a first plasticmaterial and a second plastic material, the first plastic material beinggenerally rigid and the second material being generally elastomeric.

Preferably, wherein the first plastic material is overmoulded with thesecond plastic material.

Preferably, the volute comprises an upper volute and a lower volute, thelower volute incorporating the air-inlet. Preferably also, the lowervolute includes feet moulded from the second plastics material.

Preferably, the upper volute incorporates the air-outlet. Preferablyalso, the upper volute includes a seal constructed from the secondplastic material and which in use is adapted to provide a seal betweenthe upper and lower volutes.

In one embodiment the upper and lower volutes are adapted to besnap-fitted together.

A further form of the invention provides a flow generator case for aflow generator used in delivery of breathable gas to a patient, saidflow generator case comprising a shell of rigid plastics overmouldedwith an elastomeric lining.

Preferably, said elastomeric lining forms external feet of said flowgenerator case.

A further form of the invention provides a fan support arrangement for aflow generator used in delivery of breathable gas to a patient,including a fan housing containing a motor and fan, said supportarrangement including a plurality of mounting springs, wherein saidsprings, fan housing, motor and fan form a spring system having anatural resonant frequency less than one tenth of the frequency of alowest operating speed of said fan.

A further form of the invention provides a flow generator unit fordelivering breathable gas to a patient, including a flow generator casehaving an air outlet, a fan volute contained within said case, furtherincluding a flexible tube connecting an outlet of said fan volute tosaid air outlet, said flexible tube having two or more corrugationstherein.

A further form of the invention provides a flow generator and humidifiercombination for continuous positive airway pressure treatment of apatient, including a flow generator and a humidifier removably attachedto the flow generator, wherein said flow generator includes a humidifierattachment detector including an optical transmitter and an opticalsensor and wherein said humidifier includes an optical path connectorwhich, when said flow generator and humidifier are attached, completesan optical path between said optical transmitter and said opticalsensor.

A further form of the invention provides a muffler arrangement in an airflow path of a flow generator used in delivery of breathable gas to apatient, including a first muffler volume, a second muffler volume and aconnecting portion linking said first and second muffler portions,wherein said connecting portion is narrow relative to said mufflerportions and includes a lead-in portion which narrows in a directionaway from said first muffler portion.

Preferably said connecting portion includes a venturi.

A further form of the invention provides a handle assembly for a flowgenerator used in delivery of breathable gas to a patient, including aflow generator case, a handle including a pair of attachment arms, eachattachment arm having a projection received in a respective track ofsaid case, and a handle retention member which attaches to said case toretain said handle projections against travel along said track.

A further form of the invention provides a method of attachment of ahandle to a flow generator case, said handle including a pair ofattachment arms, each attachment arm having a projection received in arespective track of said case, including the steps of sliding saidhandle projections along respective of said tracks and attaching ahandle retention member to said case to retain said projections againsttravel along said respective tracks.

Preferably, said sliding of said handle projections along said trackoccurs without substantial distortion of said attachment arms.

A further form of the invention provides a humidifier for deliveringhumidified breathable gas to a patient, including a humidifier case,

-   -   a water container,    -   a heater located in heat transfer communication with said water        container,    -   a gas flow path including a gas inlet, a humidified gas outlet        and an intermediate gas flow path which contacts the gas with        water vapour from said container,

-   further including a drainage opening adjacent said heater allowing    drainage of water past the heater to exit said humidifier case.

A further form of the invention provides a humidifier for deliveringhumidified breathable gas to a patient, including

-   -   a humidifier case,    -   a water container,    -   a heater pad located in heat transfer communication with said        water container,    -   a gas flow path including a gas inlet, a humidified gas outlet        and an intermediate gas flow path which contacts the gas with        water vapour from said container,

-   wherein said heater pad has an upper heating surface and a    peripheral heating surface which includes a side wall of said heater    pad, and wherein a heat transfer surface of said water container is    shaped to correspond to said heater pad so as maintain close heat    transfer communication with said upper heating surface and    peripheral heating surface of said heater pad.

Preferably, said water container defines a water volume which extendsboth above and below a level of said heating pad upper heating surface.

A further form of the invention provides a humidifier for deliveringhumidified breathable gas to a patient, including

-   -   a humidifier case having a hinged lid,    -   a water container adapted for drop-in assembly in said case,    -   a heater in heat transfer communication with said water        container,    -   a gas flow path including a gas inlet, a humidified gas outlet        and an intermediate gas flow path which contacts the gas with        water vapour from said container,

-   wherein said water container has a gas passage inlet communicating    with said gas flow path,

-   said humidifier further including a gas passage inlet seal for    sealing connection said gas passage inlet to said gas flow path,    wherein said sealing connection is actuated by drop-in assembly of    said water container and hinged closing of said lid.

Preferably, said gas passage inlet is located on a rear face of saidwater container and aligns with a gas passage aperture on an opposedface of said case.

A further form of the invention provides, in a humidifier assembly for aflow generator used in delivery of a supply of breathable gas to apatient for treatment of sleep disordered breathing, the humidifierassembly comprising a water tub having an inlet, a base having a bloweroutlet and a water-tub-receiving-portion, and a hinged lid with anengagable locking mechanism, a method of forming a seal between thewater tub inlet and the blower outlet of the base comprising the stepsof:

-   -   placing the water tub in the tub-receiving-portion of the base        so as to position the inlet and the outlet adjacent one another;    -   closing the hinged lid; and    -   engaging the locking mechanism.

Preferably, the blower outlet includes front-facing seal formingsurface, and the step of placing the water tub in thewater-tub-receiving portion of the base further includes the step ofplacing the water tub against the seal forming surface of the bloweroutlet.

A further form of the invention provides, in a humidifier assembly for aflow generator used in delivery of a supply of breathable gas to apatient for treatment of sleep disordered breathing, the humidifierassembly comprising a water tub having an air outlet and an hinged lidwith an engagable locking mechanism and an air delivery portion adaptedto mate with an air delivery conduit so that the supply of breathablegas can be provided to a patient interface, a method of forming a sealbetween the water tub air outlet and the air delivery portion comprisingthe steps of:

-   -   closing the hinged lid; and    -   engaging the locking mechanism.

Preferably, the hinged lid has an underside, and the underside includesa seal forming surface comprising a removably attachable gasket.

A further form of the invention provides a humidifier assembly for aflow generator used in delivery of a supply of breathable gas to apatient for treatment of sleep disordered breathing, the humidifierassembly comprising a water tub having an air inlet and an air outlet, ahumidifier base having a blower outlet and a water-tub-receivingportion, and a lid having an air delivery portion adapted to mate withan air delivery conduit so that the supply of breathable gas can beprovided to a patient interface, wherein said water-tub-receivingportion and water tub have complementary formations adapted to guidedrop-in positioning of said water tub to align said air inlet with saidblower outlet.

Preferably, said complementary formations further guide positioning ofsaid water tub to align said air outlet with a position of said airdelivery portion of said lid when said lid is closed.

A further form of the invention provides a humidifier for deliveringhumidified breathable gas to a patient, including

-   -   a humidifier case having a lid,    -   a water container within said case,    -   a heater in heat transfer communication with said water        container,    -   a gas flow path including a gas inlet, a humidified gas outlet        in said lid and an intermediate gas flow path which contacts the        gas with water vapour from said container, and    -   a gas outlet seal operatively associated with said lid whereby        closing said lid creates a sealed communication between said        humidified gas outlet the seal and a gas space of said water        container.

Preferably, the humidifier further includes a gas passage seal attachedto the underside of said lid cooperating with a surface of said watercontainer to form a sealed gas passage between a gas passage inlet and agas inlet to said gas space.

Preferably also, said gas outlet seal and said gas passage seal areintegrally formed.

A further form of the invention provides a humidifier for deliveringhumidified breathable gas to a patient, including

-   -   a water container,    -   a heater in heat transfer communication with said water        container,    -   a gas flow path including a gas inlet, a humidified gas outlet        in said lid and an intermediate gas flow path which contacts the        gas with water vapour from said container,    -   wherein said intermediate gas flow path includes a gas passage        between a gas passage inlet and a gas inlet to said gas space,        said gas passage having a floor sloping downwards from said gas        passage inlet to said gas inlet.

Preferably, said gas passage includes a drainage portion below a levelof the gas passage inlet, being a forwardmost portion of said gaspassage having a front wall below the level of the gas passage inlet.

A further form of the invention provides a humidifier for deliveringhumidified breathable gas to a patient, including

-   -   a water container,    -   a gas flow path including a gas inlet, a humidified gas outlet        in said lid and an intermediate gas flow path which contacts the        gas with water vapour from said container,

-   wherein said gas flow path is adapted to introduce said gas into a    headspace of said water container with a swirling motion.

Preferably, said intermediate gas flow path includes a container airinlet adapted to introduce gas generally tangentially into saidcontainer headspace.

Preferably also, said intermediate gas flow path includes an arcuate gasflow path leading to said container air inlet, and further includes acontainer air outlet positioned generally centrally of said headspace.

A further form of the invention provides a control circuit for ahumidifier for delivering humidified breathable gas to a patient,including a user operable control for selecting a desired gas humiditysetting and a heater control circuit for determining a target heatertemperature corresponding to the humidity setting and controlling aheater to attain said temperature, wherein said user operable controlincludes an off setting for which said heater control selects a targetheater temperature less than a lowest operating temperature of saidhumidifier.

A further form of the invention provides a control circuit for ahumidifier for delivering humidified breathable gas to a patient,including a user operable control for selecting a desired gas humiditysetting and a heater control circuit controlling a heater current to avalue corresponding to the humidity setting, said user operable controlincluding setting a reference voltage in response to said user operablecontrol and amplifying said voltage to control said heater current.

A further form of the invention provides a flow generator for deliveringbreathable gas to a patient, including a processor, a timer, user inputmeans and a display, said processor being programmed to receive areminder request input and to generate a reminder display at a timespecified in said reminder request input.

Preferably, said processor is adapted to cancel a reminder request uponreceiving a cancellation input from said user input means.

Also described herein are improved, modular, devices for enabling dataconnection with the apparatus, including the connection of data storagedevices such as memory cards, smart cards, communication ports and thelike to be selectively attached by the user or by medical personnel.

A further form of the invention provides a modular data or electricalconnector arrangement for a flow generator unit for deliveringbreathable gas to a patient, including:

-   -   a flow generator case including an aperture;    -   a gas flow generator;    -   a control circuit for said flow generator, said circuit        including a connector positioned to be accessible through said        aperture for data or electrical communication with an external        device; and    -   a plurality of closure modules each adapted to attach to said        case to cover said aperture, at least one of said closure        modules including an internal connector adapted to connect with        said control circuit connector, an external data or electrical        port adapted for connection to said external device and a data        or electrical pathway between said internal and external        connectors.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the invention will now be described withreference to the accompanying illustrations, which show a presentlyproposed embodiment.

In the drawings:

FIG. 1 is a general view of breathable gas apparatus embodying thevarious features of the invention;

FIG. 2 is a general view of the flow generator of the apparatus;

FIG. 3 is a general view of the humidifier unit;

FIG. 4 is a cutaway view of the flow generator;

FIG. 5 is an exploded view of components of the flow generator;

FIG. 6 is a vertical transverse cross-section of the flow generator;

FIG. 7 is a more detailed illustration of the bottom case and powersupply of FIG. 5;

FIG. 8 is a more detailed illustration of the chassis, chassis lid andfan housing of FIG. 5;

FIG. 9 is a more detailed illustration of the PCB, top case and exteriorfittings of FIG. 5;

FIG. 9A is a schematic vertical cross-section detail of the connectionof the handle to the flow generator top case;

FIG. 10 is an underneath view of a chassis forming part of the flowgenerator;

FIG. 11 is a vertical cross-section of the chassis through a venturipassage connecting muffler cavities of the flow generator;

FIG. 12 is a general view of a fan forming part of the flow generator;

FIG. 13 is a vertical cross-section showing the fan mountingarrangement;

FIG. 14 is an exploded view of a humidifier adapted for use with theflow generator of FIG. 5;

FIG. 15 is a rear view of the humidifier assembly;

FIG. 16 is a perspective of a seal for the air flow path;

FIG. 17 is an underside perspective of the humidifier lid of FIG. 14;

FIGS. 18 and 19 are respectively a perspective and a detail crosssection of the humidifier lid seal of FIG. 14;

FIGS. 20 and 21 are respectively a perspective and a longitudinal crosssection of the humidifier tub lid of FIG. 14;

FIG. 22 is a graph of heater target temperature against humidifiersetting;

FIG. 23 is a schematic circuit diagram of a power control circuit to thehumidifier heater;

FIG. 24 illustrates reminder menus of the flow generator control; and

FIGS. 25, 26, 27, 28, 29, 29A, 30, 31, 32, 33 and 34 show variousmodular data connector arrangements;

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The illustrated apparatus comprises a flow generator 50 and a humidifier150, shown in their assembled condition in FIG. 1, and separately inFIGS. 2 and 3 respectively. As shown in FIG. 2, the flow generatorengages with the separable humidifier at an engagement face 52, fromwhich protrudes an air connector 53 for the delivery of air from the fanto the humidifier container, electrical connectors 54 for the deliveryof power to the humidifier heater and an optical coupling transmitter200 and sensor 201 described further below.

The face 52 also carries a pair of slots 55 which are engaged bycorresponding tongues 156 provided on the humidifier engagement face 157(FIG. 15) by which the flow generator 50 and humidifier 150 areconnected together, as will be described in more detail below.

Flow Generator

Externally, the flow generator 50 is also provided with an LCD screen 58and associated keys 59 by which the user can set the operatingparameters of the unit.

Flow Generator Case

The flow generator 50 has an external case of rigid plastics materialmoulded in two parts, a top case 60 and a bottom case 61. The lower edgeof the top case 60 is stepped and flanged at 62 (FIG. 9) to mate withthe periphery of the bottom case 61.

With reference to FIG. 7, the bottom case 61 of flow generator 50 has ashell 120 of rigid plastics material, such polycarbonate/ABS blend,forming the structure of the case, integrally overmoulded with a lining121 of an elastomer such as a synthetic rubber or thermoplasticelastomer which forms the seal 63 between the top and bottom cases andthe chassis 64 and also forms the external feet of the case (see FIG.6). The lining 121 also covers the internal surface of thechassis-receiving cavity of the bottom case and the dividing wall 123between the power supply cavity 65 and chassis-receiving cavity, theresulting composite of the rigid shell with elastomeric lining servingto reduce radiated noise levels from the flow generator by dampingacoustic resonance of the walls.

Formed in the bottom case 61 by walls which join the outer wall of thecase are the lower parts and of, respectively, a power supply cavity 65and a first muffler cavity 134. The upper parts of these cavities areformed by the chassis 64, described below.

The first muffler cavity forms part of the air flow path from the airinlet 85 to the blower, receiving air from an air inlet path defined bythe chassis 64, as described below.

The chassis 64 forms the blower or fan cavity 70, inlet and outlet airflow paths and the top of the power supply cavity 65. The fan cavity 70includes a metal liner tub 73 insert moulded into the chassis asdescribed below.

Flow Generator Chassis

The chassis 64 is formed with a peripheral wall 69 flanged around itslower edge to engage with the inner periphery of the overmoulded sealingflange 63. The chassis 64 includes a downwardly extending fan cavity 70in which is mounted the fan 90 described below. This cavity 70 is formedby moulded side walls 71 and base 72, which are formed by moulding innerand outer layers of thermoplastic around an inserted steel liner tub 73.The tub may be stainless steel, nickel plated mild steel or othersuitable corrosion resistant metal. The fan cavity 70 opens to the uppersurface of the chassis 64 to enable insertion of the fan 90, thisopening being closed by a lid 74.

The density and stiffness of the steel tub creates a highly effectivebarrier to transmission of the motor and fan noise, while formation ofthe cavity 70 by insert moulding from differing materials provides veryeffective acoustic damping, as does the combination by co-moulding ofthe hard and soft plastics described already and further describedbelow. In this aspect of the present invention, the use of co-mouldingor overmoulding in the combination of materials of different, preferablywidely different, stiffness and different, preferably widely different,density has been found to be particularly advantageous in providingacoustic damping.

Preferred materials for the chassis and liner tub are polypropylenethermoplastic for the chassis and metal, preferably steel (optionallystainless steel), for the liner tub. The applicant has found that byforming the fan cavity as a composite of metal and polymer—having adifferential in density of greater than 5 times, preferably about 7-8times, and also significantly different stiffness and dampingproperties—the resonance peaks of the composite structure are welldamped so that noise generated by the fan is well-suppressed by the fancavity construction.

It is especially preferred that the polymer for the chassis 64 be aglass fibre-filled polymer containing from 10-40%, and more preferablyabout 30%, glass fibre. The Applicant has found that the use of thismaterial as a composite with a steel liner tub 73 gives both effectivedamping of fan noise and a good match in thermal expansioncharacteristics so that the composite material chassis performs wellover a wide range of operating temperatures. Further, the Applicant hasfound that the use of glass fibres outperformed talc, bronze, glass beadfiller materials for this purpose.

The top of the fan cavity is formed by the chassis lid 74, which isformed of an embedded steel insert overmoulded with elastomer to provideacoustic damping and sealing of the top of the fan cavity 70 A preferredpolymer lining for the lid is an elastomer, for example of the same typeused for the lining 121 of the bottom case.

Again, the use of a steel and polymer composite creates an effective andwell-damped barrier to transmission of fan and motor noise.

Drop-In Power Supply

The upper part of the power supply cavity 65 is formed by a side wall 75extending downwardly from the roof of the chassis 64, which sealinglyengages the opposed wall of the lower portion of this cavity.Preferably, the lower wall is provided for this purpose with aco-moulded or overmoulded rubber sealing flange 76. The power supplycompartment is thus sealed against the ingress of moisture from theinterior of the unit in the case of backflow from the humidifier.Similarly, the air path is sealed from the power supply compartment. Theinterior is at the same time acoustically sealed from the power supplycavity, which may not be completely sealed from the exterior, due to thenecessity of providing mains power input and low voltage power output tothe humidifier, via connectors 77 and 79 mounted in apertures 78 and 80respectively in the rear and front walls of the cavity, and if necessarythe venting of the compartment to outside air for cooling. This reducesassembly time and allows the overall device to be smaller.

With reference to FIG. 7, a power supply unit 124 is received in thepower supply cavity 65, for providing electrical power for operation ofthe fan, control functions and the humidifier heater pad. The powersupply comprises a printed circuit board 133, to which are directlyattached by soldering or other suitable means a power inlet connector77, a fan power outlet connector 126 for the fan motor and a humidifierpower outlet 79. Each end of the power supply cavity 65 has mountingguides 136 for supporting the PCB of the power supply in an uprightposition so that installation of the power supply is achieved by drop-inassembly. By rigid attachment of the connectors by soldering direct tothe PCB, the need for connection of wiring looms to the PCB iseliminated and the connectors align with respective ports in the bottomcase 61 when the power supply is inserted.

PCB

With reference to FIG. 8, the fan 90 and fan housing 93, 94 fit into thefan cavity 70 of the chassis and connect to electrical connector 26 atthe top of the power supply PCB. Elastomer overmoulding of the base 94of the fan housing seals the housing, provides acoustic damping of thefan housing base and forms feet on the bottom of base to act as bumpstops protecting the fan in case the unit is bumped or dropped.

As shown in FIG. 9, supported on the top of the chassis 64, in the spaceformed between the chassis and the top of the top case 60, is a printedcircuit board 81 carrying the electronic control components of the unit.The printed circuit board 81 preferably includes an LCD display 58.Optionally, at the rear of the board an edge connector 1082 and asliding connector 1082A may be accessible from a connector aperture inthe rear of the case 60, providing for modular connector arrangements tobe described in more detail below with reference to FIGS. 25 to 34.

Air Inlet Path and Mufflers

Also provided in the rear wall of the top case is an air inlet 84, andthis communicates with an air inlet passage 85 formed in the chassisabove the roof of the upper portion of the power supply cavity 65, thispassage in turn opening to first muffler cavity 134 surrounding thebottom of the fan cavity of the chassis.

The top case further defines an air inlet to the flow generator, and hasa replaceable filter 129 of any suitable material, such as foam orfibre, and filter cover 130 fitted to the top case 60. An inlet wedge131 serves as an airflow guide. A blank cover 132 clips in place overapertures in the case which align with connectors 1082, 1082A to provideports on the PCB for communications, etc. Further details of thecommunications and/other electrical ports in the flow generator casewill be described later with reference to FIGS. 25 to 34.

From the first muffler volume 134 under the fan cavity 70, inlet airpasses through a connection passage 137 (FIG. 11) into a second mufflervolume formed by the space between the fan cavity 70 and the fan.

The fan cavity and the space between the bottom case and the chassisthus form a pair of serially connected volume mufflers, with arestricted diameter passage therebetween. Noise attenuation produced bya muffler system is generally proportional to the ratio of arepresentative diameter of the muffler volume to that of theconstriction, and thus an optimal muffler design must balance optimalnoise attenuation against the constraints of available mufflervolume—especially in a compact machine—and avoiding unacceptable airflow restriction through the constriction.

The Applicant has found that a favourable adjustment of this balance maybe achieved by forming the intermediate connecting passage 137 betweenthe muffler volumes as a venturi, as shown in FIGS. 10 and 11, with arelatively short, smoothly varying diameter lead in portion 137 a at theend adjacent the first muffler, an intermediate constriction 137 b and agradually expanding lead out portion 137 c at the downstream end. Inthis way, the muffler system can achieve the noise attenuation accordingto the representative diameter of the smallest diameter portion, withbetter pressure drop characteristics.

Fan

It will now be convenient to describe the features of the fan, which areshown in FIGS. 12 and 13.

The fan 90 comprises a motor 91, preferably brushless DC motor, providedwith a coaxial impeller 92, mounted vertically within a fan housingconsisting of a cover 93 and a base 94. An air inlet 95 is provided inthe floor of the base 94 on the impeller axis, and cavities in the coverand base form a volute 96 which leads from the impeller to an air outlet97. The cover and base 93 and 94 are joined by means of slotted tabs 98which extend upwardly from the base to snap over stepped ribs 99, thetabs 98 being further located by fitting between parallel ribs on thecover 93. The joint between the cover 93 and the base 94 is sealed by anelastomeric over- or co-moulded sealing ring 101.

The bottom surface of the fan housing base 94 is provided with radialstiffening ribs, and overmoulded to the base 94 is an elastomer dampingmember 103 which covers that bottom surface between the ribs, andextends around the edge of the base by a flange portion and peripherallyspaced tabs. By overmoulding to the rigid plastics base 94 an elastomerof much lower stiffness substantial acoustical damping is provided tothe fan housing.

Moulded integrally with the rigid plastics portion of the fan housingbase are feet 106 which extend proud of overmoulded elastomer member 103to receive helical mounting springs 102 (FIG. 13), preferably of metal,by which the fan is mounted on the base 72 of the fan cavity.

The degree of size reduction which is an objective of the presentinvention requires great care to be taken to minimise the transmissionof noise and vibration, particularly from the motor and the impeller ofthe fan 90. The mounting springs are therefore chosen to ensure minimaltransmission of the vibration frequencies encountered during operation.This is achieved by choosing the springs with reference to the mass ofthe fan 90, such that the natural frequency of the system comprising thesprings and the fan is less than approximately one tenth of the shaftspeed of the motor when running at its lowest operating speed.

The air outlet 97, upon the introduction of the fan into the fan cavity,is connected by means of a thermoplastic elastomer or silicone rubbercoupling member 108 with an air passage which extends from the side wallof the fan cavity to a connecting nozzle 110 extending through anaperture provided for this purpose in the front face of the flowgenerator. It is preferred that the coupling member 108 includes atleast two corrugations which provide flexibility to the connection andimproved resistance against transfer of vibration from the fan to theflow generator case.

The fan 90 therefore floats within its cavity 70 in the chassis 64 withminimum acoustic coupling to the remainder of the flow generator. Thecharacteristics of the mounting springs and the coupling member 108 arechosen to minimise the transmission of characteristic vibrationfrequencies of the fan.

Further details of the fan construction and fan mounting are describedin US20030168064 and WO99/64747, the contents of which are incorporatedherein by reference.

The illustrated flow generator construction and materials combinationsare adapted to result in a compact CPAP flow generator unit of similarperformance and noise characteristics to larger units—eg. capable ofgenerating from 4-20 cmH₂O pressure and a flow rate of 120 L/min and atotal radiated noise volume of less than 33 dbA, more preferably lessthan about 30 dbA, when operating at 10 cmH₂O—in a flow generator unithaving a total volume of about 2 litres or less.

Handle Attachment

A keypad 59, facia 127 and transport handle 128 attach to the top case60.

With reference to FIGS. 9 and 9A, a novel and easily assembled handleattachment assembly is described and shown. The handle 128 has opposedarms with inwardly projecting pins 140 at their distal ends. The topcase 60 includes a pair of channel-shaped tracks 141 with one open andone closed end, for receiving respective of the pins. To assemble thehandle to the top case, the pins are inserted from the open ends oftheir respective channels and slid toward the closed ends. The facia 127clips onto the top case 60, and includes projections 142 which trap thepins 140 in the end of their tracks 141.

The handle attachment configuration thus provides a quick and simplemeans of assembly without requiring flexing of the handle arms to locatethe pins into small recesses as in the prior art.

Humidifier

As shown in FIGS. 14 to 21, the humidifier 150 comprises a base unitdesigned for simple attachment to and detachment from the flow generator50, which forms a cradle for a water container which is in turnattachable to and detachable from the base unit.

The general arrangement of the humidifier components includes a base(rear cover 803 and front cover 602) onto which is fitted a heatercomprising a heater plate (plate 632 with ceramic heater pad 800) whichsupports a water tub (tub base 698, seal 699 and tub lid 700) and ahinged humidifier lid 648 which seals against the tub lid 700 to form anair path into the tub through the tub lid.

The rear face of the base has a peripheral flange 153 which seats in acorresponding peripheral recess 113 surrounding the front face of theflow generator 50 when the two units are brought together by linearmovement towards each other. A latch 404 is held in place by latchretainer 404 a to be moveable vertically and resiliently urgeddownwardly by spring 404 b, so that the tongues 156 engage in the slots55 and snap home to engage the two units by means of the downwardlyextending fingers 158 at the ends of the tongues.

Coupling of Flow Generator and Humidifier

The PCB of the flow generator is provided at the end adjacent thehumidifier with an optical transmitter 200 which emits a periodic flashof light from the end face of the flow generator case, and an opticalsensor 201 to detect the presence or absence of the humidifier. The rearface of the humidifier contains a curved reflector 202 which, when thehumidifier is attached to the flow generator, completes an optical pathfrom the transmitter to the sensor so that the flow generator PCBdetects the presence of the humidifier and may adjust the controlalgorithms accordingly.

The rear face of the base unit also carries a connector 162, in thisembodiment a pair of flat male blade connectors, for engagement with amating connector 114 on the front face of the flow generator, to providepower to the humidifier heater from the power supply in the power supplycavity 65. Although not shown in the illustrated embodiment, therespective faces may also carry further interconnecting devices, whereother electrical or data connections are required to be establishedbetween the flow generator and the humidifier or downstream devicesincluding the air conduit or the mask. Such devices may take the form ofoptically coupled devices, or connectors of other suitable kinds.

The use of such an opto-coupling connector enables the implementation ofa simple protocol for communications between the flow generator and thehumidifier. For example, the current flow levels of the flow generatorcan be sent to the humidifier controller which then adjusts theoperation of the humidifier according to a predetermined algorithm.

In the humidifier construction, the back cover 803 which fits to therear of the front cover 602 provides the air, electrical andcommunications connections to the flow generator and provide support fora control PCB 804 and the catch assembly. The catch assembly includes alatch 404 which is retained by a latch retainer 404 a and spring 404 b,and operates to attach the humidifier to the flow generator generally asdescribed for the earlier embodiments. A control knob 805 on the top ofthe front cover 602 is connected to the PCB 804 to allow patient controlover the degree of humidification.

There is also provided an aperture 264 (FIG. 15) for electricalconnections between the humidifier and the flow generator, or forelectrical and signal connections to the humidifier.

The air port 807 in the humidifier rear face mates with the outlet 110of the flow generator.

An elastomer airway seal 722 fits between the front and back covers toconnect the air port 807 in the back cover 803 to the aperture 626 ofthe front cover 602. The seal (shown in more detail in FIG. 16) has aninlet connector portion 722 a which connects to the flow generatoroutput via the air port 807 formed in the back cover 803, and aperipheral seal portion 722 b which extends about the aperture 626periphery at the front face of the cover 602. A wall portion 722 c ofthe seal closes off a lower part of the aperture 626, leaving a smalleraperture 722 d defined by the seal.

As a result, the airway seal 722 defines a closed passage from thecircular air port 807 to the rectangular aperture 722 d in the verticalwall of the front cover.

Heater Pad

The heater pad comprises lower and upper parts 806, 800 and a heater padcover 632.

The heater pad cover 632 has an upper heating surface 634, a downwardlyextending peripheral wall 636 acting as a further heating surface and arear flange with a pair of attachment portions 640 for attachment of theheater pad to tubular protrusions 628 on the rear of the front cover602.

The heater pad cover 632 is configured to accommodate, below the upperwall 634 and within bounds of the wall 636, a heater pad or otherheating means such as an induction heater, for causing heating of thewater in the humidifier water container.

The front of the heater pad cover 632 has a forwardly extending tab 646of dog-legged shape, which extends to the front of the humidifier cradlefront cover 632 to support the heater and also provide a catch for thehumidifier lid 648.

Water Tub

The water container consists of a water tub 698, seal 699 and tub lid700.

The floor of the tub 698 is of complementary shape to the heater pad,and is formed of metal or other material suitable to conduct heat fromthe heater pad to the water in the tub. The floor has a generallyhorizontal portion 900 corresponding to the upper heating surface 634 ofthe heater pad and a U-shaped portion below the level of the heater padupper surface, including a generally vertical heat transfer portion 902below the horizontal portion corresponding to the peripheral heatingsurface. When the water container is placed in the humidifier cradle andthe hinged lid 648 closed, the water tub base is held in close contactwith the heater pad to transfer heat into the water in the tub.

By providing a part of the water tub volume and heat transfer surfaceabout the periphery of the heater pad, a similar water volume andheating area to those in prior art humidifiers can be obtained in a morecompact assembly.

As shown in FIG. 20, the rear surface of the tub lid has an air inletaperture 801 leading to an inlet end of the U-shaped air passage 718.When the humidifier lid 648 is closed, the tub 698 and tub lid 700 arepressed rearwards so that the peripheral seal 722 b abuts the rearsurface of the tub lid in a locus surrounding the rear opening of theinlet aperture 801, creating a sealed air path from the flow generatoroutlet to air passage 718 and into the headspace of the humidifier tub.This allows the humidifier tub to be removed for refilling and replacedwithout the need for a separate operation to connect the air flow.

With reference to FIG. 21, the inside wall of the tub lid 700 hasprojections 802 a, 802 b which serve to limit the press fitting of thetub lid onto the tub base 698. One projection 802 a is provided at thefront of the tub, and further projections 802 b, or sets of projections,are provided on opposed side walls of the tub lid, forward of the rearof the tub. This positioning of the projections 802 b allows one-handeddisengagement of the tub base and tub lid by squeezing together of thebase and lid at their rear end, causing the connection to pivot aboutthe side projections 802 b and the tub and lid to separate at the front.The ability to separate these components one-handed is a feature ofconsiderable utility, especially for stroke patients or other users withlimited dexterity.

As best seen in FIGS. 20 and 21, the water container lid 700 has an airpassage 718 formed as a U-shaped channel, leading to the humidified airentry aperture 720 into the headspace of the water container. Thechannel floor slopes down in the direction of air flow from the airinlet end to the end at which the air enters the water container. Thewater container lid also has an elliptical humidified air exit apertureor outlet 801.1. These air passages and apertures co-operate with thehumidifier lid 648 when closed to define the air flow paths within thehumidifier, as will be described below.

Water may be added to the water container via the air exit aperture oroutlet 801.1 while the tub lid is in place, or by removing the tub lid.

The tank is intended to be filled via the air exit aperture or outlet801.1, and the apparatus may be provided with a filling bottle with aspout dimensioned for a convenient fit with that outlet. Such a bottlemay be provided with a spout of the kind incorporating an air bleedpassage which will allow the tank to fill to the correct predeterminedheight.

In alternative embodiments, other filling arrangements may be employed,for example by removing the tub lid. The correct filling height may alsoindicated by filling level graduations scribed or otherwise marked onthe wall of the water tub.

A microswitch (not shown) or other sensing means may be provided to turnoff power to the heater pad when the lid is opened, and/or when thewater container is removed.

Humidifier Lid and Air Flow Paths

FIGS. 17 to 19 show the underside of the humidifier lid 648 and the seal676 which provides a seal to the tub lid 700 about the U-shaped passage718 and the humidified air exit aperture 716. The seal 676 comprises anedge seal portion 676 a and membrane portion 676 b, as shown in FIGS. 18and 19.

The lid 648 has an upper wall 650 and a front wall 652 which extendsdownwards, and outwardly, from the upper wall. The upper wall 650 has arecess at its rear side, such that the part of the upper wall and frontwall 652 on each side of the recess constitutes a rearwardly projectingarm 656. At the rearmost extremity of each arm 656 there is an inwardlyprojecting hub 658. The hubs 658 are configured to be received in thesockets 622 of the humidifier front cover 602 such that each hub and itscorresponding socket constitute a hinge connection, for attaching thelid 648 to the front cover.

During opening of the lid 648, it may be freely rotated about the hubsthrough greater than 90° until it reaches a maximum extent of normaltravel. The lid and front cover are configured such that, if the lid isthen rotated further, the hubs pop out of the sockets 622. This may beachieved, as would be understood by a person skilled in the art, byproviding suitable chamfers on the hubs and/or sockets, or othersuitable formations on the lid or cover, so that the lid flexes torelease the hubs from the sockets.

The lower edge of each arm 656 is shaped complementarily to the shape ofthe upper portion of the face of the front cover to accommodate thatpart of the arm when the lid 648 is in a closed position.

The lid 648 includes a humidified air outlet pipe 662 which passesthrough the upper wall 650 and extends upwards and forwards at an acuteangle from the top of the upper wall, for attachment of a hose to supplyhumidified air to a patient. The pipe 662 continues below the lowersurface of the upper wall 650 to define an elliptical rim 664.

Extending downwards from the lower surface of the upper wall 650 is awall 666 which is configured to define a closed path and hence aU-shaped enclosed region 668 within the confines of the wall.

At the front extremity of the front wall 652, that is, adjacent thelower edge of that wall, there is provided a recessed notch 674 on therear (inner) surface of that wall, for snap-fit engagement with the tab646 of the heater pad cover to act as the catch for the lid. The lid maybe opened by flexing the assembly to release the tab from the notch.

Attached to the lid 648 is an elastomer lid seal 676, which isillustrated in FIGS. 18 and 20. The edge seal portion 676 a of the lidseal includes a channel 676 c which fits over the wall 664 and rim 666on the bottom of the lid 648, and a curved sealing flange 676 d whichseals against the top surface of the tub lid, so that the space betweenthe U-channel 718 on the tub lid and the seal membrane forms an inletair passage of the tub, and the air exit aperture or outlet 801.1 of thetub lid communicates via the elliptical opening 676 e in the lid seal tothe air outlet pipe 662 of the humidifier lid 648. This is achievedwithout the need to connect and disconnect air tubes to remove the watercontainer.

As the air supplied from the flow generator is under pressure, thispressure assists the sealing flange 676 d of the sealing member 676 tocreate a firm seal around the recess 718 by forcing the extensionportion outwards and downwards. A similar effect is created on the sealsurrounding the elliptical aperture 716 in the tub lid due to thepressure of the air exiting the water receptacle.

Once the air from the flow generator passes into the water container,the air then travels across the surface of the water so that the airbecomes humidified. The heating of the water by the heating pad enhancesthis humidification. The air then exits the water container through theoutlet opening 716 to the air outlet pipe 662, which is in turn attachedto a suitable hose (not shown) for supplying the humidified air to apatient.

By providing the air inlet to the water tub headspace via an arcuatepath, the air mass within the container is caused to swirl and thusenhance the uptake of water vapour from the water contained in the tub.

The enhanced uptake of water vapour achieved by inducing the swirling ofair as it passes through the tank enables, in an alternative embodimentof the invention, the elimination of the heating of the water in thetub. In such an embodiment the heating element and its controls, and theheat transfer components including the heating plate and the metal tankbase are eliminated, and the humidifier becomes a simpler, passive,device.

A humidifier assembly in accordance with the present invention has anumber of advantages over the prior art. One advantage relates toconvenience of use. Convenience of use is important for all patients,especially those who have poor dexterity.

The base of the humidifier assembly includes a generally “negative”U-shaped channel. The bottom portion of the water tub has acorresponding “positive” U-shape. The outer wall of the U-shape issloping, whereas the inner wall is generally vertical. Because the baseand water tubs have complementary configurations, placing the water tubgenerally in the correct position means that it will to some extentself-align into the correct position, which as described below, is asealing position.

A water tub according to the present design can be easily placed in asealing position without requiring a patient to connect small fiddlytubes such as used in the prior art. An aspect of this is that a seal isprovided by placing a generally flat surface such as the rear of thewater tub, or the top surface of the water tub, against respectivesilicone gaskets that present a corresponding flat surface. Therespective seals are formed when the two flat surfaces contact. Thus thehumidifier assembly has a very convenient “drop-in” configuration.

The water tub is held in position by the simple motion of swinging thepivoting lid through approximately 90° from fully open to closed. Thelid is locked in position via a robust mechanism which provides andaudible and reassuring “click”-sound when engaged. Whilst in thepreferred embodiment, a pivoting movement is used for the lid, othermovements are contemplated including sliding and translation.

The lid of the humidifier assembly includes an air delivery tubeconnector, which in a preferred form is generally cylindrical.Connection of the air delivery tube to the lid can be achievedregardless of whether the water tub is in position. This arrangementmeans that the water tub can be removed and refilled with water ifnecessary without requiring disengagement of the air delivery tube fromthe humidifier assembly.

The illustrated humidifier construction provides a compact humidifieradapted for ease of manufacture and use, and further provides protectionagainst backflow of water into the flow generator when the humidifierand flow generator units are assembled together. Backflow protection isprovided by the sloping floor of the air passage and the location of theair inlet aperture 801 and the aperture 722 d in the seal 722 relativeto the air inlet 720 from the air passage 718 into the headspace of thehumidifier tub 698. In particular, if the tub is overfilled while in itshorizontal position, the water will flow back along the U-shaped airpassage 718 only as far as its forwardmost portion, which has a frontwall 717 lower than the air inlet aperture 801, and will drain towardsthe front of the machine. If the machine is tipped up onto its rear, thewater will be prevented from flowing back along the air passage from thetub to the air inlet 801 as the intermediate portion of the air passage718 will be above the level of the aperture 720. The water will thenflow back into the tub once the machine is righted.

If the machine is tipped onto its side, either the air inlet aperture720 or the air inlet 801 will be above the water level and thus watershould not flow back into the low generator. Again, any water whichescapes the tub will flow back into the tub once the machine is righted.

If desired, further security against backflow can be provided bylocating a non-return valve at an appropriate point, for example aflexible membrane supported in the mouth of the humidifier air inlet.

In addition to those features and advantages already described, thecomponents and features of the humidifier according to the presentembodiment have various advantages.

By providing the top seal to the water receptacle as part of thehumidifier lid, improved simplicity of use is achieved while minimisingthe risk of spillage of water. In addition, the contour of the lid sealis adapted to collect condensation which may form in the lid cavity andthe headspace of the water receptacle, preventing backflow of thiscondensation to the flow generator when the lid is opened.

Furthermore, the configuration of the front and back covers of thehumidifier and of the heater pad is adapted to allow fitting together ina vertical orientation, to minimise the need for reorientation duringassembly of the humidifier unit on the production line.

In addition, the resilience of the connection between the lid and thewater receptacle, provided by the lid seal, is adapted to maintaindownwards pressure on the water receptacle when the lid is closed, tomaintain good heat-transfer contact between the base of the waterreceptacle and the heater pad without the added complexity and expenseof spring-loaded mounting of the heater pad.

Humidifier Power Supply

The humidifier is provided with a control knob allowing adjustment ofthe humidity of the air supply to the patient. With increasing humiditysetting, the temperature of the water container is increased byproviding increased power to the heater, to raise the humidity of theair leaving the humidifier. The control knob may have a smoothlyvariable control, or a series of discrete humidity settings, and willhave an ‘off’ setting where no power is supplied to the heating pad. Thecorrelation between the humidity setting and the power to the heater iscontrolled by a circuit on the PCB 804.

FIG. 22 is a sketch of a preferred calibration curve of target watercontainer temperature (y axis) against humidity setting (x axis),including upper and lower tolerances.

At the left hand end of the correlation curve, corresponding to the lowhumidity settings and the off position of the control knob, the heatercontrol selects a very low target heater temperature—less than ambienttemperature, and preferably lower than the lowest operating temperatureof the humidifier. In this way, the heating is turned off when thecontrol knob is in its off position, while allowing use of a lessexpensive potentiometer without an integral off switch or a separateon/off switch. The mounting of the control knob mechanism may provide atactile ‘click’ at the off position of the control knob, to confirm tothe user that the heater is turned off

FIG. 23 is a circuit diagram of the humidifier control circuit forcontrolling the water temperature, including a potentiometer POT1actuated by the control knob 805 and an operational amplifier OA1providing power to the heater 800.

A potentiometer may be used in series with the heating element to setthe operating temperature. However, this may result in large heat lossesthrough the potentiometer as in the following equation

P=V ² /R

where V=the supply voltage and is normally fixed and R=RH+RP where RH isthe resistance of the heater and is fixed and RP is the resistance ofthe potentiometer which is variable and provides the temperaturecontrol. The current is: I=V/R, and the proportion of heat through thepotentiometer is I²*RP=RP*V²/(RP+RH)². The remainder of the heat is usedby the heater element to heat the water.

These heat losses in the potentiometer require large heat dissipationsurfaces to prevent overheating.

In the present embodiment, the potentiometer is used in the control pathof a semiconductor arrangement to set the operating temperature. Thissubstantially reduces the current through the potentiometer because thepotentiometer now only carries a semiconductor control current ratherthan the load current required to drive the heater element.

In a preferred embodiment, the potentiometer is used in conjunction witha temperature sensing element to control an operational amplifier whichdrives the heater directly or through a high current semiconductorswitch.

FIG. 23 shows an arrangement for controlling temperature via anoperational amplifier OA1.

The operational amplifier n1 has a pair of inputs, V+ being an addinginput and V− being a subtracting input. The output of the amplifier isproportional to the difference between the voltages on the inputs V+ andV−.

Input V− is connected to a reference voltage determined by the ratio ofresistors R21 and R17;

Vref=Vs*R12/(R12+R17)

The temperature of the water is sensed by temperature sensitiveresistive element, thermistor TH1, and the operating point is set bypotentiometer POT1. The operational amplifier input V+ is connected tothe junction of R106 and thermistor TH1. The operational amplifierswitching threshold is determined by the ratio of the resistance of thepotentiometer POT1 plus resistor R106 to the resistance of theresistance network formed by thermistor TH1 plus resistor R11 inparallel with resistor R10 plus resistor R10 equals the ratio ofresistor R17 to resistor R21. That is, the operational amplifierswitches when the junction between the thermistor TH1 and resistor R106crosses over the potential at V−.

The operational amplifier is powered from supply points Vss and Vo, sothe drive current does not pass through the potentiometer. Vss may bethe same as Vs, and Vo may be the same as 0 v. The operational amplifiermay drive the heater element directly or it may control a powertransistor which drives the heater element.

This arrangement significantly reduces the dissipation through thepotentiometer, allowing a smaller potentiometer, with smaller coolingneeds, to be used. The arrangement is also well adapted for use inimplementing the ‘soft’ off setting arrangement described above withreference to FIG. 22.

Reminder Menu

FIG. 24 is a flowchart of a Reminder menu to set a number of remindersto alert the patient to specific events; for example, when to replacetheir mask, when to insert a Data Card (if their device is Data Cardenabled) and so on. It can also be used to set special customisedreminders.

When a reminder is due, a message is displayed on the LCD and remainswhenever the device is not delivering therapy. The backlight on the LCDflashes when a message is displayed. If more than one reminder for apatient is scheduled for the same date, all scheduled reminders aredisplayed during that day. A patient can clear a message by pressing theLEFT key (or inserting a Data Card, in the case of the Data Cardreminder).

The default setting for all reminders is that they are disabled. To usethe reminder menu, the patient enters the Reminder Menu from the standbyscreen by pressing LEFT and DOWN for at least three seconds.

FIG. 24 summarises the Reminder Menu screens:

REPLACE MASK—to set a timed reminder to remind a patient when they needto replace their mask. The patient can press the LEFT (clear) key toremove the message from the LCD.

CALL PROVIDER—to set a reminder for the patient to phone the therapistat a certain time; for example,to discuss how their therapy is going.The patient can press the LEFT (clear) key to remove the message fromthe LCD.

INSERT CARD—if a patient's flow generator is Data Card enabled, thetherapist can set a timed reminder on the flow generator to remind themthat they need to insert a Data Card to transfer patient data. Thisenables the therapist to establish compliance. The patient shouldactually insert the Data Card in order to clear the message from theLCD. (They can also press the LEFT (clear) key to remove the message.)

REPLACE FILTER—to set a timed reminder to remind the patient when toreplace the air filter. The patient can press the LEFT (clear) key toremove the message from the LCD.

FIGS. 25 to 32 are rear views of the flow generator, showing variousforms of modular data connections foreshadowed earlier, utilising theslot 83 in the rear of the flow generator housing.

With reference to FIG. 25, the slot 83 is provided in the wall of arectangular recess 1115. An arcuate depression 1123 is provided in theupper surface of the unit above the recess 1115 to facilitate removal ofclosure elements from the depression, as described below.

At the rear of the printed circuit board 81, an edge connector 1082 anda sliding connector 1082A are aligned with and accessible through theconnector slot 83 in the rear of the case 60, providing for the modularconnector arrangements to be described in more detail below.

Where, as shown in FIG. 26, the flow generator in question is notintended to be employed with any data connection, the slot 83 is closedoff by a blank closure element 132, shaped to fit into the recess 1115.The closure element is shown in more detail in FIG. 27. This elementsnaps into the recess by means of lower tabs 1118 and an upper tab 1119which fit corresponding depressions such as 1122 in the walls of therecess 1115, to close the slot 83 and conform to the contours of thesurrounding surface of the unit.

Complementarily shaped closure elements can be provided for thereception of different kinds of data devices. Shown in FIG. 28 is anelement 1116 a provided with a slot for the reception of a smart card1120. The element 1116 a or the printed circuit board itself may carrythe necessary smart card socket.

Shown in FIG. 29 is a closure element 1116 b provided with a DB typedata socket. In this case the element 1116 b is contoured to provide alower front recess 1121 to facilitate gripping of the associated plug. Across-section of a modified form of this arrangement is shown in FIG.29A, illustrating the connection between the internal connector 1086 ofthe element 1116 b and the edge connector 1082 of the PCB, and theexternal DB9 connector 1088.

Other forms of element 1116 can be provided to enable the connection ofdevices such as memory cards and pre-programmed devices as required.This facility furthermore enables a wide range of devices to beintegrated with the apparatus in modular fashion, for example a clockdisplay which may utilise the system clock contained in the flowgenerator controller, a voice activation unit, oximetry, ECG and otherdiagnostic aids, a sound recorder, a light.

FIGS. 30 to 32 are a series of rear perspective views of the flowgenerator, illustrating one embodiment of the modular data connectorarrangement. FIG. 33 shows the front, inner surface of the USB closureelement module, and FIG. 34 is a vertical cross-section of the flowgenerator.

FIG. 30 shows the slot 83 open, exposing the edge connector 1082 andsliding connector (not visible in this view) at the rear of the flowgenerator PCB 81. The connectors 1082, 1082A comprise a plurality ofelectrical contacts for carrying data and/or power between the PCB andan external device.

FIG. 31 shows the arrangement of FIG. 31 where no data connection isrequired, with the slot covered by a blank closure element 132 generallyas described above with reference to FIGS. 25 to 27.

FIG. 32 shows a removable closure element module 1116 c carrying astandard universal serial bus (USB) port 1084 on its rear surface. Theelement 1116 c incorporates an electrical/data pathway to an electricalconnector 1090 at its forward, inner surface (FIGS. 33 and 34) adaptedto connect with all or selected ones of the contacts of the PCBconnector 1082 for electrical and/or data transmission. The closuremodule 1116 c has internal electrical components completing a dataand/or electrical pathway between its internal and external connectorsso that the module acts as an adaptor between the PCB connector and astandard USB port.

By providing the modular data connection arrangements as describedabove, in which a plurality of interchangeable connection modules fit toone or more fixed, standard connectors on the PCB, the cost and size ofthe flow generator unit may be reduced as the unit may be provided withonly those connectors which are needed by that patient, and additionalconnector modules supplied only if the need arises. Furthermore, thearrangement facilitates upgrade of the data connection arrangement ofthe flow generator to keep up with technological advances or changes inglobal data connection standards.

In this specification, the word “comprising” is to be understood in its“open” sense, that is, in the sense of “including”, and thus not limitedto its “closed” sense, that is the sense of “consisting only of”. Acorresponding meaning is to be attributed to the corresponding words“comprise, comprised and comprises where they appear.

While particular embodiments of this invention have been described, itwill be evident to those skilled in the art that the present inventionmay be embodied in other specific forms without departing from theessential characteristics thereof. The present embodiments and examplesare therefore to be considered in all respects as illustrative and notrestrictive, the scope of the invention being indicated by the appendedclaims rather than the foregoing description, and all changes which comewithin the meaning and range of equivalency of the claims are thereforeintended to be embraced therein. It will further be understood that anyreference herein to known prior art does not, unless the contraryindication appears, constitute an admission that such prior art iscommonly known by those skilled in the art to which the inventionrelates.

1. A flow generator unit for delivering breathable gas to a patient,including: a flow generator case; a powered gas flow generator withinthe case; a power supply unit adapted for drop-in assembly in said case,said power supply unit including a printed circuit board, a power inputconnector rigidly attached to said printed circuit board and a poweroutput connector, and a power supply unit mounting for mounting saidpower supply unit in said case such that said power input connectoraligns with a power input port of said case.
 2. A flow generator unitaccording to claim 1 wherein said power input and power outputconnectors are attached directly to said printed circuit board.
 3. Aflow generator unit according to claim 2 wherein said power input andpower output connectors are soldered directly to said printed circuitboard.
 4. A flow generator unit according to claim 1 wherein said powersupply unit is received in a power supply compartment of said case, saidpower supply cavity being sealed against ingress of any liquid presentin a flow generator compartment of said case.
 5. A blower enclosure fora flow generator used in delivery of breathable gas to a patient, saidblower enclosure including a metal container overmoulded with anacoustically damping polymer lining,
 6. A blower enclosure according toclaim 5 wherein said polymer comprises polypropylene.
 7. A blowerenclosure according to claim 6 wherein said polymer includes from 10-40%glass fibre.
 8. A blower enclosure according to claim 7 wherein saidpolymer includes about 30% of said glass fibre.
 9. A blower enclosureaccording to claim 8 wherein said glass fibre-filled polymer has similarthermal expansion characteristics to said metal container.
 10. A blowerenclosure according to claim 5 wherein said metal container is a steeltub.
 11. A blower enclosure according to claim 5 wherein said polymerlining is overmoulded onto inner and outer surfaces of said metalcontainer.
 12. A blower enclosure according to claim 11 wherein saidpolymer lining of said container inner surface includes formations forengagement of a motor housing.
 13. A blower enclosure for a flowgenerator used in delivery of breathable gas to a patient, said blowerenclosure being adapted to reduce noise from the enclosed blower, saidenclosure comprising: (i) a cavity within a chassis of the flowgenerator, the cavity defined by side walls and base, the enclosurebeing adapted to receive and mount a blower in said cavity; and (ii) alid adapted to be mounted on said chassis so as to form a top surface ofthe cavity, wherein at least one of the chassis and lid is moulded froma composite comprising a metal and a plastic.
 14. A blower enclosure asclaimed in claim 13, the metal and the plastic being adapted to havegenerally similar coefficients of thermal expansion.
 15. The blowerenclosure of claim 13 wherein the metal and plastic are co-moulded. 16.The blower enclosure of claim 13 wherein the metal is nickel-plated mildsteel.
 17. The blower enclosure of claim 13 wherein the plastic ispolypropylene.
 18. The blower enclosure of claim 17 wherein thepolypropylene includes a glass
 19. A blower enclosure according to claim18 wherein the glass filling is glass fibre.
 20. A blower enclosureaccording to claim 19 wherein said polypropylene includes from 10-40%glass fibre.